I look for a natural material, preferably organic, that adsorb phosphorus. The adsorption capacity can be low as compared to mineral materials like slag or apatite. The point is to have something disposable like soil.
The bone mill is a good source of phosphorus, if you decompose the bone marrow with the mustard oil cake and cow dung for 1 month in a regular intervals of mixing it will release the phosphate and a it is a liquid manure it can be easily intakeable for plants.
Other than that you can use the rich phosphate but it takes time to release but not soluble in water. But the solubilization can be increased with a special ash from an advanced organic practice called Agnihotra in this method the ash is created if mixed with soil the solubilization increase in a very remarkable way. For further information and the process of Agnihotra you can refer the below link